1. Field of the Invention
The invention relates to a power supply system, and more particularly to a power control circuit thereof.
2. Description of the Related Art
Power supply and energy savings are important issues for electronic and electrical appliances. In a conventional power supply system, a power supply is directly connected to a voltage converter, which converts a supply voltage of the power supply to a desired voltage and supplies the desired voltage to an electronic device, such as a chipset of the electronic device. When the power supply is plugged in, there is power consumption even though the system is switched off or is not performing its primary function (for example, in a standby mode). This kind of power consumption, which is also called ‘standby power consumption’, may be caused by the power supply (which converts AC voltages into DC voltages), circuits and sensors that receive remote signals (such as a Wake-on-LAN signal), and soft keypads and displays that include LED status lights. For saving energy, the standby power consumption of devices is limited to be within a specific range; especially in developed countries having more stringent standards. Accordingly, power loss is an important issue for power supply systems.